I have a WM72, but I guess it's similar.
Withdraw the machine and remove the top (3 screws at rear and then slide backward)
You should then be able to see a large clip which secures the seal to the drum, this will need to be slackened for removal.
Open the loading door and you will note a plastic spring clip at the 12 o'clock position. Unlock this clip to reveal the steel wire clip which holds the front of the seal to the machine body.
With both items removed you should easily be able to remove the old seal. Fitting the new seal is a reverse of the above procedure.
Takes about half an hour.